Air preheater



June 20, 1933.

W. F. KEENAN, JR, ET AL AIR PREHEATER Original Filed Jan. 24, 1930 VvV - perature of .air to be Patented June 20, 1933 wn'raa 1-. menu,:12... or ranmm warnmrn, or rmwoon, roaurron, or new xoax, 1:.

H1303, NEW NEW JERSEY,

Y, A CORPORATION OF NEW YORK YORK, nu) JOSEPH swarm! asslonoas 'roros'rna wnanmm coam l mina-ma Original application filed January 24,

1980, Serial No. 483,051. Divided and this application filed [arch in,1981. Serial Ro.,524,832.

This application is a division of our copending application Serial No.423,051, filed January 24th, 1930.

Our invention relates to air preheaters and more particularly to airpreheaters for heating air for combustion in a boiler plant by means ofthe products of combustion or flue gases leaving theboiler plant.

Amongst the objects of the invention are: to provide means forregulating the flow of air through an air preheater so as to maintainproper temperature conditions; to prevent formation of moisture withinan air 'preheater; to selectively feed air to dif- I ferent .sectionsofan air preheater to obtain predetermined temperatures of fluids; tocoordinate the flow of air to the flow of products of combustion throughan air preheater so as to obtain desired temperatures of heated airand'to obtain desired temperatures of products of combustion; toregulate air. flow through an air preheater so as to obtain desired andpreferably constant temsupplied to fuel pulverizing apparatus and likedevices; to automatically regulate ,the flow of air through an airpreheater; to automatically regulate the flow of air through an airpre-v heater to obtain desired conditions of temperature and to preventformation of moisture within an air preheater; to provide an airprehcater in combination with a plurality of paths or conduits for flowof air to a furnace and to regulate the relative quantities of airflowing in the various paths to obtain the best operating conditions;and other objects as will appear.

The nature and advantages of the invention and the various phasesthereof will become apparent from consideration of the followingspecification taken in conjunction with the accompanying drawing which 7forms a part of this specification, and on which:

' Fig. 1 is a side or elevational view of an air. 'preheater embodyingthe invention; and

Fig. 2 is a cross-sectional, horizontal view taken on the line 2-2 ofFig. 1.

The air preheater is indicated, in general, by reference character 10.It comprises bustion pass through four sections, tion comprises sidewalls 15 and 16. Within each section are partitions 17 consisting ofvertically arranged parallel plates. The plates are arranged to formalternate spaces separated fromeach other. For this purpose the latesare joined at the sides as shown in ig. 2 in pairs, and each plate of apair is joined at the top to the adjacent plate of the next pair, asshown for examglae, in U. S. Patent No. 1,727 ,124, granted gtember 3rd,1929, to William Lonsdale. etween the sections are intermediate conduitsor sections 19 which connect corresponding spaces of the difierentsections to permit flow of fluid, specifically gas, serially through thesections, vertically, in one set of alternately disposed spaces. Thesides of the sections are connected by intermediate conduits or returnbends 20, connecting the other set of spaces for serial flow of fluidhorizontally through the sections. .It will be seen that the gases (air)flowin horizontally are separated from the gases products of combustion)flowing vertically downward; Products of combustion are supplied to theair preheater at the top throu h connection 21 and flow straight downwarly through all the sections of the air preheater, passing through theconnections 19 into and through the soot hopper 34 and thence into theflue 35. 7

Referring to Fig. 2, the products of comthe spaces 24. Air is admittedto the preheater by means of the lower conduit 23, passes transverselythrough section 14, thence through the intermediate conduit 20connecting section 14- with section 13, thence transversely throughsection 13, thence through the right-hand conduit 20, thencetransversely through'section 12, thence through the upper left-handintermediate conduit 20, thence transversely through the upper section11 and thence to the boiler in which'the heated air is to be used.Referring further to Fig. 2, it will be seen that the air asses throughthe spaces 22. It will also seen that the air and the products ofcombustion do not come into direct contact.

11, 12, 13 and 14. Each sectages in that the heat I at certain .l

Eeroducts of combustion would be lowered to 27 presence of moisture,

With the arrangement thus fardescribed, wherein roducts of combustionpass through al of the sections of the air preheater Fug air rob b htionsote air eater itispossilet at (wi the temperature of the low whatis known'as the dew-point, at which point of temperature, steam, carriedin the products of combustion, condenses and recipitates. It isdesirable to avoid the owerlng of the temperature of the products ofcombustion to the dew-point in order to prevent preci itation ofmoisture, particularly with certain fuels of high sulphur content, sincewater and the sulphur dioxide resultin from the combustion of such fuelscombine to form sulphuric acid, which is highly corrosive. Corrosioncauses uneven surfaces of metal. With moisture present, ash in thedproducts of combustion tends to deposit an form a sticky mass on theuneven surface produced by corrosion. Such sticky deposit may form adistinct coating on the metal and may causefurther deposits. The passaes of air preheaters are small in order. to 0 tain eiiiciency of heattransfer and in order to economize on space. The formation of suchdepositsidue to the corrosion and ash content of the products ofcombustion may materially diminish the cross-sectional'area of flow inthe passages between the plates of the preheater, that is, betweenpartitions 17.

rrosion itself is undesirable because it decreases the life of aparatus, but, in this case, there is the added disadvantage of thedliacreasel1 of Th d f t e re eater is ecrease o flow in ea carrie swith it several disadvantransfer capacity of the plates is reduced; thedraft loss is increased, as a result of which more power is of plantsalready equipped with the preheater at a sutlicient rate.

necessary to operate the fan to draw the gases through the preheater;and, in the case fans of given capacity, the accumulation of depositsmay reduce the capacity of the steam generating unit due to theinability of the fans to draw the products of combustion through Toovercome this diiiiculty we have provlded a by-pass conduit 25, a damperor valve 26 in by-pass' con :lult 25, and a damper or valve 27 intheintermediate conduit 20 between sections 13 and 14. By-pass conduit 25connects the air supply conduit 23 with the intermediate conduit 20between sections 12 and 13. By closing damper 22- and opening damper 26,all the air to be heated passes directly to section 12. -Damper may beused to prevent recirculation of air around sections 18- and 14 when thedamper 26 is open. By partially opening damper 26 and having damper 2'?open, or

passes through all of the or in para and cross-sectional area of flow of0 products of combustion partially open, some of the air will pass throb all the sections and some will pass only ugh two sections. Theproportion of air passing through all sections and bypassing somesections can be regulated by proper manipulation of the dampers 26 andIf the air is cold or if other conditions prevail such that there is alowering of the temperature of the products of combustion to or below'the dew-point, the air can be passed through by-passconduit 25 in wholethus a temperature can be maintain in the outlet for of combustion whichis above the dewint.- By regulating the dampers it is possi le to obtaina constant temperature in the products of .combustion leav' the air preheater, or in any degree, 31m limitations, of variation of temperaturedesired, independentl or in spite of variations of load.

It wil be readily seen that one or more of the sections may be b -passedin this way. The conduit 25 may be connected between conduit 23 and theair inlet for section v13, or even with the air inlet for section' 11.

The damper 26 may be interconnected with the damper 27 and they may beautomatically controlled in accordance with the temperature of productsof combustion leaving the reheater.

t wil be understood that variations may be made within the spirit andscope of the invention; g

What we claim is: e 1 Apparatus for heating air by products f com ustioncomprising a plura i nected to form two sets of separated spaces meansto connect .the sections for flow o serially. through the sections inone set of separated spaces, lateral return bends connecting thesections for passage of air serially through the sections in the otherset of separated spaces, an air supply conduit, an air discharge conduitmeans tos'uppl combustion, a yconnection between the air su ply con uitand one of the return bends, and a damper in said by-pass connection.

2. A paratus for heating air by products I of com ustion comprising aplura i of sections, each having closely sp plates connected to form twosets of se arated spaces, means'to connect the sections or flow ofproducts of combustion serially through the sections in one set of searated spaces, lateral return bends connecting the sections for passa ofair serially through the sections in 0 other set 0 separated spaces,

an air supply conduit, an air discharge conduit, means to supply anddischarge products of combustion, a by-pass connection bethe products tyof sectime, each having closely spaced pla'tesconand discharge productsof tween the air supply conduit and a return bend connected to the nextto the last section in the line of flow of roducts of combustion, and adamper in said iy-pass connection.

3. Apparatus for heating air b products of combustion comprising a pluraity of sections, each having closely spaced plates connected to form twosets of separated spaces, means to connect the sections for flow of mproducts of combustion serially throu sections in one set of'separatedspaces, ateral return bends connecting the sections for passage of airserially through the sections in the other set of separated spaces, anair supply conduit, an air discharge conduit, means to supply anddischarge products of combustion, a y-pass connection between the airsupply conduit and the return bend connecting the second and thirdsections in the line of air flow, a damper in said by-pass connection,and means to cut ofi flow through the return bend connecting the firstand second sections in the line of air flow. a

4. Apparatus for heating air by products of combustion comprising aplurality of sections, each having closely spaced plates connected toform two sets of separated spaces, means to connect the sections forflow of products of combustion serially through the 39 sections in oneset of separated spaces, lateral return bends connecting the sectionsfor passage of air serially through the sections in the other set oilseparated spaces, and means to supply air to cheer the other or both ofthe first and third sections in the line of flow of air. 7

5. In a due gas preheater of the plate type including a plurality ofsections, the method of controlling thetemperature of flue gases leavingthe preheater which comprises sup plying air to the one or the other orboth of the first and third sections in the line of air flow to maintainthe temperature of the flue gases above the dew point. p 6. Apparatusfor heating air by products of combustion comprising a plurality ofsections, each section having a passage for the flow of products ofcombustion therethrough and a passage for the flow of air therethroughout of contact with said products of combustion, means for connectingthe sections so that the products of combustion flow serially throughthe several sections, conduits connectin the sections and the airpassages so that t e air flows serially through the several sections, anair supply conduit, an air discharge conduit, means to sup ly anddischarge products of combustion, a bypass connection between the airsupply conduit and one of the conduits connecting said air passages, adamper in said by-pass connection, and a damper for controlling the flowof air through the conduit connecting the air passages in the sectionswhich are 6e by-passed.

h the' 7. Apparatus for heating air b products of com ustioncomprising aplura ity of sections, each section having a passage for the flow ofproducts of combustion therethrough and a passage for the flow of airtherethrough out of contact with said products of combustion, means forconnecting the sections so that the products of combustion flow seriallythrough the several sections, conduits connecting the sections and theair passages so that the air fiows serially through the severalsections, an air supply conduit, an air discharge conduit, means tosupply and discharge products of combustion, and means to supply air toone or the other or both of two sections separated by one or more othersections.

8. In a flue gas prcheater having a plurality of sections, each providedwith a passage for the flow of products of combustion therethrough and apassage for the flow of air therethrough out of contact with theproducts of combustion, the products of combustion and air passagesrespectively of the several sections being connected in series, methodof controlling the temperature of flue gases leaving the preheater whichcomprises supplying air to two sections separated by one or more othersections to maintain the temperature of the due gases above the dewpoint.

In testimony whereof, we have hereunto afiixed our signatures.

WALTER F. KEENAN, da.

JOSEPH STANLEY W ETHERALD.

the

till

